Variable pitch screw propeller articulated blade mounting



R. DOUSSAIN ETAL 2,660,252

VARIABLE PITCH SCREW PROPELLER ARTICULATED BLADE MOUNTING 5 Sheets-Sheet 1 Filed May 1, 1947 INVENTORS W 3141011 'I ATTOR EYS Nov. 24, 195 3 R. DOUSSAIN ETAL VARIABLE PITCH SCREW PROPELLER ARTICULATED BLADE MOUNTING Filed May 1, 1947 '5 Sheets-Sheet 2 Nov. 24, 1953 R. DOUSSAIN ETAL 2,660,252

VARIABLE PITCH SCREW PROPELLER ARTICULATED BLADE MOUNTING Nov. 24, 1953 R. DOUSSAIN ETAL 2,660,252

VARIABLE PITCH SCREW PROPELLER ARTICULATED BLADE, MOUNTING Filed May 1, 1947 5 Sheets-Sheet 4 Nov. 24, 1953 DOUSSMN ET AL 2,660,252

VARIABLE PITCH SCREW PROPELLER ARTICULATED BLADE MOUNTING Filed May 1, 1947 5 Sheets-Sheet 5 66 75 r 70 I I I7? van fans:-

fim W {cu-14pm .7 M+W it blades.

Patented Nov. 24%, 1953 UNITED STAT-ES PTENT OFFICE VARIABLE PITCH SCREW PROPELLER ARTICULATED BLADE MOUNTING France Application'May 1, 1947, Serial No. 745,360 Claims priority,application France May 9, 1946 9 Claims. (Cl. 170-46056) 1 This invention relates to articulation mountings for connecting to a hub a propeller blade angularly movable with respect to said hub.

It is known that at present the development of turbo-jet propulsion units forc'es'the manufacturers of conventional motor propelled equipmentmaking use of screw propellers, to improve their material in order to cope with the increastremely light. On the contrary the conventional moto-propulsive units are compelled, in the field where they-still can compete with power jet engines, to have propellers of very large diameters or else propellers having a great number of This leads to an increase of the weight of .these'parts causinga reduction of the useful load which can be transported.

It is, therefore, an object of this invention to provide an improved articulation mounting fora propeller blade permitting substantially decreasing the weight of the blades and also reducing the reaction forces applied to the hub as a result of aerodynamic and centrifugal forces," with substantial reductionalso of the weight of the hub. -In carrying out these objects the articulation mounting comprises a universal joint between the blade, and the hub of the propeller and independ.

ent means for absorbingthe forces acting in the directionof the axis of the blade, said independent means being so constructed that said articu- I of the blades (gravity and-inertia forces due, to .cen'trifugaland tangential accelerations) and on the other hand on the aerodynamical reactions 2 blade cross-section, and consequently of its weight, necessary to resist these efforts, attempts have been made to make propellers in which the axis of a blade is offset angularly'in the direction of the resultant of centrifugal and aerodynamical forces acting on the same. The direction of this inclination and its amplitude are generally determined by the maximum load.

'With such a propeller rotating at a constant predetermined speed the bending moments due to aerodynamical forces are nullified and it is possible therefore to decrease the. size of the cross-section of the blades and consequently their weight. However, very often the possibility of reducing the stresses in a blade is only theoretical, as for all otherspeeds .of operation these stresses are increased due precisely to said inclination of the blade.

adapted to be used to produce a braking action on the plane by the reversal of the pitch of the m blades which results in a reversal of the bending moment exerted onthe bladesdue to aerodynamical reactions. This reversal of the bending moment and the difliculty .of compensation by a fixed inclination of the blade axis upon the con,- struction of propellers results practically in b an increase of the weight of propellers instead of a decrease thereof; It can be mentioned also that propellers made of wood or of other light materials require increase of'cross-sections of the blades, resulting in a considerable reduction of aerodynamic efficiency of propellers and that finally the use of hollow blades made of 'materials of great stress resistance is' not interesting except for propellers exceeding certain size and mass production.

forth more clearly the. advantages which may be obtained by the use of the new articulation mounting, it may". be useful to recall the forces acting on a propeller blade.

' These forces depend on onehand'on the mass in general requires acostly toolingwhich cannot be amortized if the manufacture isn'ot based on g It seems therefor'e that the ideal solutioncone jsistsinm'akin'g propeller'blades automatically adjustable 'atanytime following the direction'of' the. resultant of aerodynamic forces producing bendi "ling moments and the actionof centrifugalfor'ces.

which constitute the very essence of a propeller operation.

; Generally,-j ifv one considers a 1 propeller "operat ing at. a constant speed, it can be determined j that the main stresses, at any point of a blade, are due to centrifugal forces which translate themselves into-tensile stresses and tobending momentsdue to aerodynamical reactions.

In ordertoavoida too great increase-ofjthe However, this; principle of free'oscillatin-g blades 'withautoma'tic compensation, whilst having been applied for: a longtime toblades of helicopters and the like has not'been used industrially in relation with'screw propellers, ventilators or similar apparatus, principally due to the importance ofcentrifugal forces acting'on the. ar-

ticulation mounting of such blades; 1

This is particularly ap- 7 parent in the. case of modern screw propellers at 12p R. P. M. is subjected to a tensile stress due to centrifugal forces of the order of 2 tons at maximum, whilst in the case of an airplane propeller made of Duralumin, of 4 meters in diameter and of a weight per blade, of 40 kgs., the propeller rotating at 1200 R. P. M., the tensile stress developed under the action of centrifugal forces is 50 times greater and may attain 100 tons. It can be easily understood that such efforts lead inevitably to heavy structures and make illusory any possibility of reduction of the weight of the blade.

The improved articulation mounting according to the invention may be applied equally to propellers with fixed pitch as well as to propellers with a. variable pitch, the axes of articulation forming a Garden suspension which may be connected either to the hub or to a blade. For instance, in the case of a variable pitch propeller with axes of articulation connected to the hub, a blade may be mounted in a sleeve in which it can rotate and which in its turn will be adapted to oscillate with respect to the hub,'the pitch variation of the blade being controlled by a second oscillating coupling concentric With respect to the first.

The above and other objects and features of the invention will be better understood from the consideration, of the following description and the annexed drawings showing, by way of an example only and solely for the purpose of explanation, certain embodiments, of the articulation mounting according to the invention applied to screw propellers with oscillating blades.

On the drawings Figure 1 shows in section made perpendicularly to the axis of rotation of the propeller a blade root and its oscillatory mounting in the hub socket;

Fig. la' is a section taken on the line II of Fig. 1;

Figure 2 is a section made following line AB of Fig. 1 and showing the universal articulation;

Figure 3 is a section made following line CD of Fi 1;

Figure 3a is a similar viewto that of Fig. 3 and showing a modified structure; v

Figure 4 is a detail view showing the manner of attachment of flexible connectors to the blades; c I

Figure 5 is a section. similar to that of Fig. 1 showing another form of embodiment; X

Figure 6 is a section made following axis EF of Fig. 5; V

Figure 7 shows another-modified construction Figure 8 is a section view taken on the line GH of Fig. '7 and,

Figure 9 shows another embodiment of the invention.

Referring now to the drawings, and beginning with. Figs. 1 to 4, there is shown a propeller blade i articulated about an axis X' X (Fig. 2) on an intermediary annular member 2. 'zis articulated in its turn about axis. Y'- -Y, perpendicular to axis X- -X in a sleeve 3, these two axes constitutingthus a universal mounting. Blade I is provided with two trunnijcns received into two ball bearings respectively}! and 5 secured on the intermediary member 2. This meinher is provided with two depressions in which are fitted ball bearings 8*and, 1 adapted to receive respectively two trunnions" carried by sleeve 3 (Fig. 2). Sleeve 3', as can be'seen on Fig.1, is adapted to slide in aradial direction with respect to a sleeve 8' in which it is guided by a splined connection. Sleeve "8 is made integral with, or

This member I may carry fixed thereon, a worm gear providing a pitch varying connection for the blade. This sleeve 8 is rotatably mounted in a corresponding hub socket 9 by means of two ball, or in general antifriction, bearings I0 and II whilst it is retained against movement in the radial direction by a thrust bearing l2.

Bearing ll is directly fitted in a centered depression at the inner end of the hub socket 9 and rests upon a resilient gasket l3 whilst bearing' lii is fitted in a coaxial depression provided in a thrust nut l4 screwed into the hub socket 9.

The centrifugal force is resisted by a set of cables such as shown in section on Fig. 2, a pair of such cables [5 and 16 located diametrically opposite one to the other being indicated in Figs. 1 and 2.

Each cable is secured by one of its extremities to the blade in any suitable manner. Fig. 4 show a particular manner in which these cables can be connected to the blade. In this example cable 15 for instance, terminated like 2, spoke of a bicycle wheelwith a threaded portion I! receiving a self-locking nut [8, permits establishing a connection between said cable and a strength tion of the centrifugal force, directly by the cables.

As shown in Figs. 1 and 2 the inner extremity of the blade is provided at the level of the universal mounting with a member 21 adapted to guide the cables upon oscillations of the blade.

Each of the cables, such as for example is and it, is connected at its iree extremity to a piston such as 22 and 23'. In the example shown in Fig l these pistons have either a prismatic form a shown in Fig. 3 or a'cylindrical form as shown on Fig. 3a and slid in the bottom of an encios ed space or chamber 25'.

This chamber 25 may be completely filled with an incompressible acid or else as shown iii the drawing with metallic balls of a reduced drain eter. This latter, arrangement eliminates all problems connected withthe provision of a fluid-- tight chamber. Ashas been hown by the two examples given on Figs. 3 and en the'fiexible com nectors or cables and their pistons may be arranged to lie in the: surface of a single or a pinrality of cylinders. c 7

Chamber 25 is closed by a cover 2provided with passages for guiding the cables. It; is formed in a hollow member 24 closed at one end by cover 2'6 and at-the other by a second cover'jt". Anoute'r shoulder or flange provided-on member 24 bears against theinner edge of sleeve '9 transmitsthus through the intermediary (if-said last member the forceof traction produced by centrifugal action to' thrust bearing [2. Between member 24 and sleeve 3 there is provided acompression spring 21 which is designedtoplace initially under tension the connec-ting cables.

The pistons 22-, 2 3,- etc'ghave a freely sliding fit ina generally annular chamber (or annularly disposed series of chambers, Fig. at) so that each piston is free to move vertically. The chamber in which the pisto'n's are fitted is a downward extension of the eyhndricalchamber 25' which is filled with a non-compressible material having fluid characteristics (a liquid or a mass of small metal balls). When one of the pistons, for instance piston 22, is pulled upward by its red or cable I5, it forces said material to push downward by a corresponding amount the piston 23 so that the rod or cable IE is maintained taut. Assuming that the pistons 22 and23 lie in the plane in which the blade is moving with respect to its support at any given moment, it will be understood that the said pistons will move the greatest distance and that the pistons adjacent to 22 and 23 will move progressively decreasing distances upward or downward, respectively, while the pistons equi-distant from 22 and 23 will not be moved at all.

In the example shown the pitch variation of the blade is controlled by a worm 28 driving the Worm gear carried by sleeve B; It will be noted that in case of a variation of the speed of rotation of the engine, or in response to the action of ambient medium, for instance temperature variations, the connecting cables are permitted to extend due to the sliding mounting of sleeve 3 in sleeve 8. In the example just described the universal connection is carried by the blade and rotates with this latter upon rotation of the same about its axis of pitch variation. However, as it has been indicated previously, the articulation mounting according to the invention may be applied also to variable pitch propellers with os cillating blades in which the universal connection is carried by the hub. An example of such an arrangement is shown on Figs. 5 and 6.

Referring now to these figures, blade I, as shown therein, is terminated at its root end by a threaded portion screwed into a sleeve it pro vided with an outer annular shoulder 3i which latter transmits the stresses due to the centrifugal force to a thrust bearing 32 which bears against a nut 33 screwed in a second sleeve 34. Sleeve is on the other hand mounted concentrically in sleeve 34 by means of two ball or in general anti-friction bearings 35 and 36, sleeve 34 being adapted to slide radially with respect to member All whichis adapted to oscillate with respect to hub 4! through the intermediary of a universal mounting. I At its inner extremity sleeve 30 is provided with a longitudinally grooved extension, by means of which it is mounted into a correspondingly splined extremity of shaft 31, so as to be able to slide radially along such shaft, this connection being designed to control pitch variation of the blade under the control of a bevel pinion 38 and through ,the intermediary of the universal mounting 39. The universal mounting 39 is arranged concentrically with respect to the universal mounting provided to permit oscillations of sleeve 34 with respect to the hub, this latter universal connection being indicated at lii. A spring 42 produces the initial tension of connecting cables 43, the arrangement of which is shown on Fig. 6, two diametrically opposite cables 43 and 44being indicated on said figure. These cables connect sleeve t l-to the body of hub 45; they carry at their inner extremities pistons 45 and 46 which mayslide in a common enclosed space or chamber 41 completely filled with an. incompressible fluid or, as shownv in the drawings, with metallic balls of a small diameter, the operation of this device being identical to that described with reference to Figs. 1 to 4.

Figs. '7 and 8 show a modified embodiment of the invention also applied to a propeller blade and in which a member suitably mounted on the blade bears against a system comprising an enclosed space or chamber of constant volume and variable form. On said figures, there is shown at l the blade and at 4| the hub of the propeller. The blade is provided with an annular shoulder 56 and is mounted in a universal suspension 54. This universal suspension 54is mounted in its turn in a sleeve BI adapted to slide with the interposition of a bushing 62 in the socket of hub 4!. Into the outer extremity of the hub socket there is screwed a retaining ring 50 receiving a ball bearing 5|. There is shown at 52 a chamber completely filled with an incompressible medium and cooperating with a series of circularly distributed plunger-pistons 53 against which bears shoulder 56 of the blade. There is shown at 55 a spring which applies against the root of the blade a resilient force. The pitch variation of the blade is produced by means of a worm gear 59 integral with sleeve 6| and meshing with a Worm 60. Fig. 8 shows a section made following line GI-I of Fig. 7.

Referring now to Fig. 9 there is shown at l a propeller blade and at 9 a propeller hub. The blade is mounted on a lateral projection 6d of a blade-carrying member 68 which is mounted for oscillating about a ball joint 15 supported by a central tubular member. A hollow socket member '52 is connected to hub 9 by means of lower portions 13 traversing, each with a certain amount of play. a corresponding slot 69 provided in the lateral projection 64 of blade-carrying member 53, which is also provided with pins 51 engaging the ball joints 65 carried by a member Ill supported by hub 9. The space left between the inner face of the spherical upper portion of socket l2 and the outer surface of blade-carrying member 68 is filled by a rubber body, the whole constituting a universal suspension permitting the blade to take any desired inclination.

According to the invention, the universal mounting is relieved from any stresses acting in the direction of the blade axis by said rubber body confined in the enclosed space between socket 12 and blade-carrying member 68, due to its comparative incompressibility, without pre venting oscillating movement Of the blade-carrying member 68 about ball joint 15.

It will be understood that reference to rubber .as the material used to fill certain spaces or cavities described herein, is intended to include suitably compounded natural or synthetic rubber and mixtures thereof; the rubber masses, in each instance, being operably interposed between relatively moving parts of the sockets and blades to permit rocking motion of the blades without appreciable radial displacement thereof with respect to the axis of the hub. The rubber may, desirably, be made adherent'to the surfaces enclosing it, so as to assist, to some extent, in returning the blade to its neutral position. i

In order to eliminate any risk of jamming between the lateral walls of member 88 and the edges of part 12 the thrust member ismade of two parts, one of them forming a central piston 58 and the other an annular member l i adapted to slide with respect to member 68, the displacements of said annular member being damped by means of a cavity ,or by a series of cavities of variable volume H, which cavities may be filled with rubber. In order to insure the locking of piston 68 at low speeds the device is completed by a member 16 resiliently applied against the interior side or member 68, the displacement of 7 said member 1 8 towards member 68 being limited by any suitable device, so that, upon the :centr ifugal force exceeding a certain value, member '68 is displaced out ol Contact with member ltd and becomes free to take any inclination (within the obvious limitations of the structure shown) According to another feature of the inventi'on the device limiting the displacement :of member T6 is adapted to act in response to centrifugal Iforce. Thus :as soon as the centrifugal force reaches a predetermined :value, member 16 is 'urged by said iorce in the direction of "unlocking. In the example shown this-device comprises centrifugal masses 19 mounted on arms $1) pivoted about fixed :axes and acting by levers 81 on -a flange 82 provided on :a rod 8 3 rigid tvith memher it There is shown at 84 a resilient ring urging member '75 in the direction opposite to that corresponding to unlocking.

It will be noted finally that, in order to avoid any jamming, there is left-a Lcertain play between member =68 and ring if! :provided between said member and the spherical bearing '15, as Well as between pins 116:? and spherical bearings es in order to perm-it the slidin .01 .ring 6:6 fol-lowing :axis 61.

It will be thus "understood that the invention provides "a system of propeller blade mounting which :may receive thrust forces as well as traction forces, While completely relieving th universa-l mounting of :a blade from the forces diz'rected following ;a generaldirection perpendicular to the plane of the universal mounting, these forces, in the case .of a propeller, being constituted by centrifugal forces.

Although several embodiments of the invention have been illustrated and described, various changes in the form or relative arrangement of parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is therefore to .be made to the appended claims for .a .definition of the limits of the invention.

What we claim is:

.1. An articulation mounting for connecting to -:a hub structure a propeller blade angularly movable with respect :to said hub structure about at least one axis comprising, a universal "joint between said blade :and said hub arranged to per- "mit swiveling of said blade with respect to the hub, an anchor :member for said 'blade disposed upon said hub, means for retaining said anchor .member in operative association "with :sai'dlhub against centrifugal force, and means-foranc'horing said blade 120 said "anchor member against centrifugal "force independently of said universal joint, said means I including an enclosed space of constant volume interposed between said anchor member and at least one blade :attachmentmember,;said enclosed space'being :entirely filled with a deformable .massconfined withinsaid space and of a consistency to now themanner of an incompressible liquid, the entire filling and the :incompressibility of themass together preventing any radial displacement :of said :blade away from said hub so as to .relieve said joint fr'om the :action of centrifugal force, andthe deformable character .of .said mass providing :said swiveling of the blade.

2. An (articulation amounting -for' -connecting to a propeller hub a propeller blade adapted to angularly adjust itself freely with respect to said hub about two rnutually perpendicular axes comprising, ineans for mounting said blade on said hub ior rotation about said-axes so thatthelong-i- 'itudinal axis -02 said blade can assume, under the action of forces acting thereon, amore or less banked position with respect to a general direction perpendicular to the --plane containing said axes, an anchor member for said blade disposed upon said "hub, "means for retaining said anchor member in operative association withsaid hub against centrifugal force, andm'eans for substantially relieving said axes of articulation from the action of forces actingon the blade-in the direc- :tion of its longitudinal axis away'from the said means including an enclosed space of "constant volume interposed between said anchor member and at least one blade attachment memher, said enclosed space being entirely filled with a deformable mass confined within said space bearing upon said anchor member and said hub and'of a consistency to how in the manner of an incompressible liquid, the incompresslb-ility of which prevents any radial displacement of said blade away from said hub so as to relieve said joint from the action of centrifugal force, the fluent character of the mass providing said free angular adjustment of the blade.

3. Anarti-culation mounting for connecting to a' hu-b structure a propeller blade a-ngularly movable with respect to said hub structure-compris- 'ing a socket member rotatably mounted on said hub, a Garden joint between the blade "root and said socket member adapted to transmit rotat-iona-l movement from the socket member to said blade root whi'le'permltting "free swivel movement of the blade, an anchor member .for said blade constituted by an inner transverse wall within said socket member, and means for anchoring said blade to said anchor "member including a recess within a face of said inner wall opposite said blade root, 2. flowable mass :entirely filling the space and interposed between relativelyinovparts thereof, said mass constituted by a quantity of balls of'a size to flow in the manner of an incompressible liquid Within said recess, .an outer transverse wall disposed within said'sock'et "member to completely cover said recess and having inwardly projecting central portion, said relatively movable parts comprising a plurality of plunger pistonsslidably mounted around said central portion, said plunger pistons and said central portion being contiguous withthesurface of said-deformablemass so as to confine the same within said recess, .a number of apertures 10110- vided in said inner transverse wall corresponding to the number of said plunger pistons, and means for connecting said blade to said plunger pistons through said apertures, "the arrangement being such that an radialdisplacement of said blade away from said hub is prevented by the incompressibility of said deformable mass so as .300 relieve the axes of said Cardan joint from the action of centrifugal force whilst the deformability or" saidmass .allowssa'idffree.swiuel moviement-of the blade.

4. An articulation mounting for connecting to a propeller ihub a propeller blade adapted to angularly adjust itself freely with respect to hub about two mutually perpendicularaxes comprising, means for mounting "said blade on hub 'for rotation about said two mutually perpendicular axes sothat the longitudinal axis .of said blade can assume, under the action of forces acting thereon, a more "or less banked position with respect to a general direction perpendicular to the plane containing said axes andindependent means for preventing any radial displace-- ment of said blade away'from said hub, said independent means comprising a chamber element formed in the hub and interposed between the hub and blade, said chamber element being formed in a configuration to provide cylinders and passage means interconnecting said cylinders, a plurality of pistons on the blade, said pistons arranged in a circle on the blade mounting means, the cylinders being arranged on a like circle in the hub with the pistons movably mounted therein but of such a size as to close the chamber, the chamber including the passage means being completely filled with a substantially noncompressible flowable mass constituted by a quantity of balls of such a size as to flow in the manner of an incompressible liquid, flexible connectors secured to the blade and arranged to lie approximately along the lines of a cylindrical surface the axis of which coincides with the axis of said mounting means, the opposed ends of said connectors connected to respective pistons, said connectors being of such a length as to apply pressure to said flowable mass.

5. An articulation mounting according to claim 1, in which the enclosed space comprises at least one chamber of a constant volume and of a variable form and in which the deformable mass is a rubber composition.

6. An articulation mounting according to claim 1, in which the enclosed space has the shape of a semi-spherical head and is located coaxially with the axis of the pivotal mounting means of the blade and between a member rigid with said blade and a member rigid with the hub.

7. An articulation mounting according to claim 6, in which the deformable mass is a rubber composition adhered to the walls of the enclosed spaced.

8. An articulation mounting according to claim 6, in which the enclosed space is bounded in one direction by a semi-spherical surface of the member rigid with the hub and in the opposite direction by a semi-spherical surface of the member rigid with the blade.

9. An articulation mounting of a propeller blade according to claim 4, in which there is provided an even number of said pistons, each of said pistons having a corresponding one of said pistons located diametrically opposite thereto in said circle whereby the two pistons of each pair are movable in opposite directions upon oscillation of the blade.

ROBERT DOUSSAIN. ROBERT BOUSSON. LOUIS PERRIER.

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